This invention relates to a portable x-ray exposure sensor for controlling the period of exposure of film to obtain the optimal result for the object being photographed.
Mammography is becoming more important in the detection of early carcinoma of the breast. In this regard, enhancing the quality of the mammographic image is a necessary prerequisite, if the largest number of early malignancies are to be detected. In order to enhance film quality, many factors must be controlled, one of the most important of which is film density or blackening. Despite extensive experience, operators have found it advisable to make a series of exposures of varying duration to obtain films suitable for diagnosis. Even with great care, it is sometimes necessary to recall the patient for further retakes. This occurs because of the anatomical differences between breasts, and in particular the ratio of fat to glandular and fibrocystic elements varies greatly between different breasts and this variation cannot be determined by physical examination.
The extra film exposures involve film and labor costs and the additional x-radiation imposed on the patient involves health hazards which would be desirable to avoid. An exposure controller which can provide a better accuracy of film exposure than the best operator estimates would produce savings in film costs, operator labor, and minimize the dangers that can result from excessive exposure of the patient to x-radiation.
One of the problems with previous types of x-ray exposure control devices, such as is shown in U.S. Pat. No. 2,488,315, is that they are fixed in location, complicated, not sufficiently sensitive for use with "soft" x-rays, such as are used for mammographs, and are not sufficiently effective for controlling exposure for the study of small areas.